Thermally-assisted magnetic recording head having a plasmon generator

ABSTRACT

A return path section includes first and second yoke portions and first, second and third columnar portions. The first and second yoke portions and the first columnar portion are located on the same side in the direction of travel of the recording medium relative to a wave guide core. The second and third columnar portions are located on opposite sides of a plasmon generator and connected to a shield. The first yoke portion connects a main pole to the first columnar portion. The second yoke portion connects the first columnar portion to the second and third columnar portions. A coil is wound around the first columnar portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thermally-assisted magnetic recordinghead for use in thermally-assisted magnetic recording in which arecording medium is irradiated with near-field light to lower thecoercivity of the recording medium for data writing.

2. Description of the Related Art

Recently, magnetic recording devices such as magnetic disk drives havebeen improved in recording density, and thin-film magnetic heads andrecording media of improved performance have been demanded accordingly.Among the thin-film magnetic heads, a composite thin-film magnetic headhas been used widely. The composite thin-film magnetic head has such astructure that a read head unit including a magnetoresistive element(hereinafter, also referred to as MR element) for reading and a writehead unit including an induction-type electromagnetic transducer forwriting are stacked on a substrate. In a magnetic disk drive, thethin-film magnetic head is mounted on a slider that flies slightly abovethe surface of a recording medium. The slider has a medium facingsurface facing the recording medium. The medium facing surface has anair inflow end (a leading end) and an air outflow end (a trailing end).

Here, the side of the positions closer to the leading end relative to areference position will be defined as the leading side, and the side ofthe positions closer to the trailing end relative to the referenceposition will be defined as the trailing side. The leading side is therear side in the direction of travel of the recording medium relative tothe slider. The trailing side is the front side in the direction oftravel of the recording medium relative to the slider.

To increase the recording density of a magnetic recording device, it iseffective to make the magnetic fine particles of the recording mediumsmaller. Making the magnetic fine particles smaller, however, causes theproblem that the magnetic fine particles drop in the thermal stabilityof magnetization. To solve this problem, it is effective to increase theanisotropic energy of the magnetic fine particles. However, increasingthe anisotropic energy of the magnetic fine particles leads to anincrease in coercivity of the recording medium, and this makes itdifficult to perform data writing with existing magnetic heads.

To solve the foregoing problems, there has been proposed a technologyso-called thermally-assisted magnetic recording. The technology uses arecording medium having high coercivity. When writing data, a writemagnetic field and heat are simultaneously applied to the area of therecording medium where to write data, so that the area rises intemperature and drops in coercivity for data writing. The area wheredata is written subsequently falls in temperature and rises incoercivity to increase the thermal stability of magnetization.Hereinafter, a magnetic head for use in thermally-assisted magneticrecording will be referred to as a thermally-assisted magnetic recordinghead.

In thermally-assisted magnetic recording, near-field light is typicallyused as a means for applying heat to the recording medium. A knownmethod for generating near-field light is to use a plasmon generator,which is a piece of metal that generates near-field light from plasmonsexcited by irradiation with laser light. The laser light to be used forgenerating near-field light is typically guided through a waveguide,which is provided in the slider, to the plasmon generator disposed nearthe medium facing surface of the slider.

U.S. Patent Application Publication No. 2011/0058272 A1 discloses atechnology in which the surface of the core of the waveguide and thesurface of the plasmon generator are arranged to face each other with agap therebetween, so that evanescent light that occurs from the surfaceof the core based on the light propagating through the core is used toexcite surface plasmons on the plasmon generator to generate near-fieldlight based on the excited surface plasmons.

A thermally-assisted magnetic recording head that employs a plasmongenerator as a source of generation of near-field light is configured sothat the write head unit includes a coil, a main pole, and the plasmongenerator. The coil produces a magnetic field corresponding to data tobe written on a recording medium. The main pole has an end face locatedin the medium facing surface. The main pole allows a magnetic fluxcorresponding to the magnetic field produced by the coil to pass, andproduces a write magnetic field from the aforementioned end face. Theplasmon generator includes a near-field light generating part located inthe medium facing surface. For the thermally-assisted magnetic recordinghead, it is demanded that the end face of the main pole and thenear-field light generating part of the plasmon generator be located inclose proximity to each other.

To increase the linear recording density of a magnetic recording device,it is effective to use a perpendicular magnetic recording system inwhich the direction of magnetization of signals to be written on tracksof a recording medium is perpendicular to the plane of the recordingmedium. It is also effective to increase, on the tracks, the gradient ofthe change in write magnetic field intensity with respect to the changein position along the direction in which the tracks extend, i.e., thedirection along the tracks (this gradient will hereinafter be referredto as the write field intensity gradient). These also apply to amagnetic recording device that employs thermally-assisted magneticrecording.

In order to increase the write field intensity gradient in a magnetichead of the perpendicular magnetic recording system, it is effective toprovide a shield that has an end face located in the medium facingsurface at a position near the end face of the main pole. U.S. PatentApplication Publication No. 2011/0058272 A1 discloses a technology forincreasing the write field intensity gradient by providing a bottomshield on the leading side of the main pole, the bottom shield having anend face located in the medium facing surface.

A magnetic head including a shield is typically provided with a returnpath section for connecting the shield to a portion of the main polelocated away from the medium facing surface. One or more spaces aredefined between the return path section and the main pole. The coil isprovided to pass through the one or more spaces.

Now, consider a thermally-assisted magnetic recording head configured sothat the near-field light generating part of the plasmon generator isinterposed between the end face of the main pole and the end face of theshield, and the core of the waveguide and the return path sectionintersect each other without contacting each other. A general approachto precluding the contact between the core and the return path sectionis to branch a portion of the return path section that intersects thecore into two portions so as to detour around the core and then mergethe two portions into one, as disclosed in U.S. Patent ApplicationPublication No. 2011/0058272 A1. When this approach is employed, thereturn path section is formed to include a coupling portion for couplingthe two branched portions. The coil is wound around the couplingportion, for example.

In the above-described configuration, the width of the coupling portionin the track width direction is equal to or greater than the distancebetween the respective outer ends of the two branched portions in thetrack width direction, thus being comparatively great. The coil shouldbe long in entire length if wound around the coupling portion. In thiscase, the coil has a high resistance, and consequently a high heatingvalue. This gives rise to a problem that components around the coilexpand and as a result, part of the medium facing surface protrudestoward the recording medium and may readily collide with the recordingmedium. In order to prevent this, the distance between the medium facingsurface and the recording medium could be increased. However, this woulddisadvantageously lead to deterioration in write characteristics such asthe overwrite property or to an increase in error rate.

On the other hand, in order to improve the write characteristics in ahigh frequency band, it is desirable that the main pole, the shield andthe return path section should form a magnetic path of reduced length.To achieve this, it is effective to bring the portion of the return pathsection intersecting the core into closer proximity to the medium facingsurface. Here, assume that the coil is wound around the coupling portionof the return path section. In this case, since the coupling portion iscomparatively great in width in the track width direction as mentionedabove, the coil should include one or more conductor portions locatedbetween the coupling portion and the medium facing surface and extendinglinearly in parallel to the medium facing surface (such one or moreconductor portions will hereinafter be referred to as linear conductorportion(s)). Bringing the portion of the return path sectionintersecting the core into closer proximity to the medium facing surfacecauses the linear conductor portion(s) to be narrow and long. This inturn causes the coil to be higher in resistance, so that theabove-described various problems will become more noticeable.Accordingly, in this case, it is difficult to reduce the length of themagnetic path formed by the main pole, the shield and the return pathsection.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a thermally-assistedmagnetic recording head including a plasmon generator in which anear-field light generating part of the plasmon generator is located inthe medium facing surface at a position between the end face of a mainpole and the end face of a shield, the thermally-assisted magneticrecording head exhibiting excellent write characteristics in a highfrequency band and being low in coil resistance.

A thermally-assisted magnetic recording head of the present inventionincludes: a medium facing surface facing a recording medium; a coilproducing a magnetic field that corresponds to data to be written on therecording medium; a main pole; a shield formed of a magnetic material; areturn path section formed of a magnetic material; a waveguide; and aplasmon generator. The main pole has a first end face located in themedium facing surface. The main pole allows a magnetic fluxcorresponding to the magnetic field produced by the coil to pass, andproduces a write magnetic field for writing data on the recording mediumby means of a perpendicular magnetic recording system. The shield has asecond end face located in the medium facing surface. The return pathsection connects the main pole and the shield to each other, and allowsa magnetic flux corresponding to the magnetic field produced by the coilto pass. The waveguide includes a core through which light propagates,and a cladding provided around the core. The plasmon generator includesa near-field light generating part located in the medium facing surface.

The first end face and the second end face are located at positions thatare different from each other in the direction of travel of therecording medium. The near-field light generating part is locatedbetween the first end face and the second end face. The plasmongenerator is configured so that a surface plasmon is excited on theplasmon generator based on the light propagating through the core, andthe near-field light generating part generates near-field light based onthe surface plasmon.

The return path section includes a first yoke portion, a second yokeportion, a first columnar portion, a second columnar portion, and athird columnar portion. The first yoke portion, the second yoke portionand the first columnar portion are located on the same side in thedirection of travel of the recording medium relative to the core. Thefirst columnar portion is located away from the medium facing surfaceand has a first end and a second end opposite to each other in thedirection of travel of the recording medium. The second and thirdcolumnar portions are located closer to the medium facing surface thanis the first columnar portion. The first yoke portion connects one ofthe main pole and the shield to the first end of the first columnarportion. The second columnar portion and the third columnar portion arelocated on opposite sides of the plasmon generator in the track widthdirection, and connected to the other of the main pole and the shield.The second yoke portion is connected to the second end of the firstcolumnar portion, and connected to the other of the main pole and theshield via the second and third columnar portions. The coil is woundaround the first columnar portion.

In the thermally-assisted magnetic recording head of the presentinvention, the core may have an evanescent light generating surface thatgenerates evanescent light based on the light propagating through thecore, and the plasmon generator may include a plasmon exciting partlocated at a predetermined distance from the evanescent light generatingsurface and facing the evanescent light generating surface. In thiscase, in the plasmon generator, a surface plasmon is excited on theplasmon exciting part through coupling with the evanescent lightgenerated by the evanescent light generating surface, the surfaceplasmon propagates to the near-field light generating part, and thenear-field light generating part generates near-field light based on thesurface plasmon.

In the thermally-assisted magnetic recording head of the presentinvention, the core may have a front end face facing toward the mediumfacing surface. In this case, the front end face may be located betweenthe first end face and the second end face in the direction of travel ofthe recording medium.

Where the core has the front end face facing toward the medium facingsurface, the front end face may have a first edge and a second edgeopposite to each other in the direction of travel of the recordingmedium. The first edge is located closer to the near-field lightgenerating part than is the second edge. When the front end face isdivided into two regions: a first region extending from the midpointposition between the first edge and the second edge to the first edge;and a second region extending from the midpoint position to the secondedge, the shield may overlap only the first region of the front end facewhen viewed in a direction perpendicular to the medium facing surface.In this case, the second and third columnar portions are connected tothe shield.

Where the shield overlaps only the first region of the front end facewhen viewed in the direction perpendicular to the medium facing surfaceand the second and third columnar portions are connected to the shield,the shield may include a first non-overlapping portion and a secondnon-overlapping portion that are located on opposite sides of the frontend face of the core in the track width direction when viewed in thedirection perpendicular to the medium facing surface. In this case, thesecond columnar portion is connected to the first non-overlappingportion, and the third columnar portion is connected to the secondnon-overlapping portion.

Where the shield overlaps only the first region of the front end facewhen viewed in the direction perpendicular to the medium facing surfaceand the second and third columnar portions are connected to the shield,the first end face and the second end face may be at a distance of 50 to300 nm from each other.

In the thermally-assisted magnetic recording head of the presentinvention, the first end face may be located on the front side in thedirection of travel of the recording medium relative to the near-fieldlight generating part, and the first yoke portion, the second yokeportion and the first columnar portion may be located on the front sidein the direction of travel of the recording medium relative to the core.In this case, the first yoke portion may connect the main pole to thefirst end of the first columnar portion. In addition, the secondcolumnar portion and the third columnar portion may be connected to theshield, and the second yoke portion may be connected to the shield viathe second and third columnar portions.

In the thermally-assisted magnetic recording head of the presentinvention, the first end face may be located on the front side in thedirection of travel of the recording medium relative to the near-fieldlight generating part, and the first yoke portion, the second yokeportion and the first columnar portion may be located on the rear sidein the direction of travel of the recording medium relative to the core.In this case, the first yoke portion may connect the shield to the firstend of the first columnar portion. In addition, the second columnarportion and the third columnar portion may be connected to the mainpole, and the second yoke portion may be connected to the main pole viathe second and third columnar portions.

In the thermally-assisted magnetic recording head of the presentinvention, the first yoke portion, the second yoke portion and the firstcolumnar portion are located on the same side in the direction of travelof the recording medium relative to the core, and the coil is woundaround the first columnar portion. These features of the presentinvention make it possible to reduce the entire length of the coil whilereducing the length of the magnetic path formed by the main pole, theshield and the return path section. The present invention thus providesa thermally-assisted magnetic recording head including a plasmongenerator in which the near-field light generating part of the plasmongenerator is located in the medium facing surface at a position betweenthe end face of the main pole and the end face of the shield, thethermally-assisted magnetic recording head exhibiting excellent writecharacteristics in a high frequency band and being low in coilresistance.

Other and further objects, features and advantages of the presentinvention will appear more fully from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the main part of athermally-assisted magnetic recording head according to a firstembodiment of the invention.

FIG. 2 is a perspective view showing a part of FIG. 1.

FIG. 3 is a cross-sectional view showing the configuration of thethermally-assisted magnetic recording head according to the firstembodiment of the invention.

FIG. 4 is a front view showing the medium facing surface of thethermally-assisted magnetic recording head according to the firstembodiment of the invention.

FIG. 5 is a plan view showing a coil of the first embodiment of theinvention.

FIG. 6A and FIG. 6B are cross-sectional views showing a step of a methodof manufacturing the thermally-assisted magnetic recording headaccording to the first embodiment of the invention.

FIG. 7A and FIG. 7B are cross-sectional views showing a step thatfollows the step shown in FIG. 6A and FIG. 6B.

FIG. 8A and FIG. 8B are cross-sectional views showing a step thatfollows the step shown in FIG. 7A and FIG. 7B.

FIG. 9A and FIG. 9B are cross-sectional views showing a step thatfollows the step shown in FIG. 8A and FIG. 8B.

FIG. 10A and FIG. 10B are cross-sectional views showing a step thatfollows the step shown in FIG. 9A and FIG. 9B.

FIG. 11A and FIG. 11B are cross-sectional views showing a step thatfollows the step shown in FIG. 10A and FIG. 10B.

FIG. 12A and FIG. 12B are cross-sectional views showing a step thatfollows the step shown in FIG. 11A and FIG. 11B.

FIG. 13A and FIG. 13B are cross-sectional views showing a step thatfollows the step shown in FIG. 12A and FIG. 12B.

FIG. 14A and FIG. 14B are cross-sectional views showing a step thatfollows the step shown in FIG. 13A and FIG. 13B.

FIG. 15 is a perspective view showing the main part of athermally-assisted magnetic recording head according to a secondembodiment of the invention.

FIG. 16 is a front view showing the main part of the thermally-assistedmagnetic recording head according to the second embodiment of theinvention.

FIG. 17 is a cross-sectional view showing the configuration of thethermally-assisted magnetic recording head according to the secondembodiment of the invention.

FIG. 18 is a front view showing the medium facing surface of thethermally-assisted magnetic recording head according to the secondembodiment of the invention.

FIG. 19 is a plan view showing a part of the thermally-assisted magneticrecording head according to the second embodiment of the invention.

FIG. 20 is a perspective view showing the main part of athermally-assisted magnetic recording head according to a thirdembodiment of the invention.

FIG. 21 is a cross-sectional view showing the configuration of thethermally-assisted magnetic recording head according to the thirdembodiment of the invention.

FIG. 22 is a front view showing the medium facing surface of thethermally-assisted magnetic recording head according to the thirdembodiment of the invention.

FIG. 23 is a plan view showing a coil of the third embodiment of theinvention.

FIG. 24 is a plan view showing a part of the thermally-assisted magneticrecording head according to the third embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Preferred embodiments of the present invention will now be described indetail with reference to the drawings. First, reference is made to FIG.1 to FIG. 5 to describe the configuration of a thermally-assistedmagnetic recording head according to a first embodiment of theinvention. FIG. 1 is a perspective view showing the main part of thethermally-assisted magnetic recording head. FIG. 2 is a perspective viewshowing a part of FIG. 1. FIG. 3 is a cross-sectional view showing theconfiguration of the thermally-assisted magnetic recording head. FIG. 4is a front view showing the medium facing surface of thethermally-assisted magnetic recording head. FIG. 5 is a plan viewshowing a coil of the present embodiment.

The thermally-assisted magnetic recording head according to the presentembodiment is for use in perpendicular magnetic recording, and is in theform of a slider to fly over the surface of a rotating recording medium.When the recording medium rotates, an airflow passing between therecording medium and the slider causes a lift to be exerted on theslider. The slider is configured to fly over the surface of therecording medium by means of the lift.

As shown in FIG. 3, the thermally-assisted magnetic recording head has amedium facing surface 60 facing a recording medium 80. Here, Xdirection, Y direction, and Z direction will be defined as follows. TheX direction is the direction across the tracks of the recording medium80, i.e., the track width direction. The Y direction is a directionperpendicular to the medium facing surface 60. The Z direction is thedirection of travel of the recording medium 80 as viewed from theslider. The X, Y, and Z directions are orthogonal to one another.

As shown in FIG. 3 and FIG. 4, the thermally-assisted magnetic recordinghead includes: a substrate 1 formed of a ceramic material such asaluminum oxide-titanium carbide (Al₂O₃—TiC) and having a top surface 1a; an insulating layer 2 formed of an insulating material such asalumina (Al₂O₃) and disposed on the top surface 1 a of the substrate 1;a bottom shield layer 3 formed of a magnetic material and disposed onthe insulating layer 2; a bottom shield gap film 4 which is aninsulating film disposed to cover the bottom shield layer 3; amagnetoresistive (MR) element 5 serving as a read element disposed onthe bottom shield gap film 4; two leads (not illustrated) connected tothe MR element 5; a top shield gap film 6 which is an insulating filmdisposed on the MR element 5; and a top shield layer 7 formed of amagnetic material and disposed on the top shield gap film 6. The Zdirection is also a direction perpendicular to the top surface 1 a ofthe substrate 1.

An end of the MR element 5 is located in the medium facing surface 60facing the recording medium 80. The MR element 5 may be an elementformed of a magneto-sensitive film that exhibits a magnetoresistiveeffect, such as an anisotropic magnetoresistive (AMR) element, a giantmagnetoresistive (GMR) element, or a tunneling magnetoresistive (TMR)element. The GMR element may be of either the current-in-plane (CIP)type in which a current used for detecting magnetic signals is fed in adirection generally parallel to the plane of layers constituting the GMRelement or the current-perpendicular-to-plane (CPP) type in which thecurrent used for detecting magnetic signals is fed in a directiongenerally perpendicular to the plane of layers constituting the GMRelement.

The parts from the bottom shield layer 3 to the top shield layer 7constitute a read head unit. The thermally-assisted magnetic recordinghead further includes an insulating layer 8 disposed on the top shieldlayer 7, a middle shield layer 9 formed of a magnetic material anddisposed on the insulating layer 8, and a nonmagnetic layer 10 formed ofa nonmagnetic material and disposed on the middle shield layer 9. Theinsulating layer 8 and the nonmagnetic layer 10 are formed of alumina,for example.

The thermally-assisted magnetic recording head further includes a shield11 formed of a magnetic material and disposed on the nonmagnetic layer10, and an insulating layer 12 disposed on the nonmagnetic layer 10 andsurrounding the shield 11. As shown in FIG. 2, the shield 11 has asecond end face 11 a located in the medium facing surface 60, a rear endface 11 b opposite to the second end face 11 a, and a top surface 11 c.The shield 11 includes a central portion 11A, and further includes afirst side portion 11B and a second side portion 11C located on oppositesides of the central portion 11A in the track width direction (the Xdirection). The length of the central portion 11A in the directionperpendicular to the medium facing surface 60 is constant regardless ofposition in the track width direction. The maximum length of each of theside portions 11B and 11C in the direction perpendicular to the mediumfacing surface 60 is greater than the length of the central portion 11Ain that direction. The distance from the medium facing surface 60 to anarbitrary point on a portion of the rear end face 11 b of the shield 11that is included in the central portion 11A decreases with increasingdistance from the arbitrary point to the top surface 1 a of thesubstrate 1. The insulating layer 12 is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes awaveguide. The waveguide includes a core 14 through which lightpropagates, and a cladding provided around the core 14. As shown in FIG.2 in particular, the core 14 has a front end face 14 a facing toward themedium facing surface 60, an evanescent light generating surface 14 bserving as a top surface, a bottom surface 14 c, and two side surfaces14 d and 14 e. The front end face 14 a may be located in the mediumfacing surface 60 or at a distance from the medium facing surface 60.FIG. 1 to FIG. 5 show an example in which the front end face 14 a islocated in the medium facing surface 60.

The cladding includes cladding layers 13, 15 and 16. The cladding layer13 lies on the shield 11 and the insulating layer 12. The core 14 lieson the cladding layer 13. The cladding layer 15 lies on the claddinglayer 13 and surrounds the core 14. The cladding layer 16 is disposedover the evanescent light generating surface 14 b of the core 14 and thetop surface of the cladding layer 15.

The core 14 is formed of a dielectric material that transmits laserlight to be used for generating near-field light. The laser lightemitted from a laser diode (not illustrated) enters the core 14 andpropagates through the core 14. The cladding layers 13, 15 and 16 areeach formed of a dielectric material that has a refractive index lowerthan that of the core 14. For example, the core 14 may be formed oftantalum oxide such as Ta₂O₅ or silicon oxynitride (SiON), whereas thecladding layers 13, 15 and 16 may be formed of silicon dioxide (SiO₂) oralumina.

The thermally-assisted magnetic recording head further includes: aplasmon generator 17 disposed above the evanescent light generatingsurface 14 b of the core 14 in the vicinity of the medium facing surface60 and lying on the cladding layer 16; and a dielectric layer 18 lyingon the cladding layer 16 and surrounding the plasmon generator 17. Theplasmon generator 17 is configured to excite surface plasmons on theprinciple to be described later. The plasmon generator 17 is formed of,for example, one of Au, Ag, Al, Cu, Pd, Pt, Rh and Ir, or an alloycomposed of two or more of these elements. The dielectric layer 18 isformed of the same material as the cladding layers 13, 15 and 16, forexample. The shape of the plasmon generator 17 will be described indetail later.

The thermally-assisted magnetic recording head further includes anonmagnetic metal layer 19 disposed on the plasmon generator 17 and thedielectric layer 18, and a dielectric layer 20 disposed on thedielectric layer 18 and the nonmagnetic metal layer 19. Each of thenonmagnetic metal layer 19 and the dielectric layer 20 has an end facefacing toward the medium facing surface 60 and located at a distancefrom the medium facing surface 60. The distance from the medium facingsurface 60 to an arbitrary point on the end face of each of thenonmagnetic metal layer 19 and the dielectric layer 20 increases withincreasing distance from the arbitrary point to the top surface 1 a ofthe substrate 1. The nonmagnetic metal layer 19 functions as a heat sinkfor dissipating heat generated at the plasmon generator 17 outward fromthe plasmon generator 17. The nonmagnetic metal layer 19 is formed ofAu, for example. The dielectric layer 20 is formed of the same materialas the cladding layers 13, 15 and 16, for example.

The thermally-assisted magnetic recording head further includes aninsulating layer 21 lying on the plasmon generator 17, the nonmagneticmetal layer 19 and the dielectric layers 18 and 20, and a main pole 22lying on the insulating layer 21 such that the plasmon generator 17 isinterposed between the main pole 22 and the core 14. The main pole 22has a first end face 22 a located in the medium facing surface 60. Theinsulating layer 21 is formed of the same material as the claddinglayers 13, 15 and 16, for example. The shape of the main pole 22 will bedescribed in detail later. The thermally-assisted magnetic recordinghead further includes a second columnar portion 23, a third columnarportion 24 and a second yoke portion 25 each formed of a magneticmaterial. The second yoke portion 25 is at a predetermined distance fromthe main pole 22 and lies on the insulating layer 21. The second yokeportion 25 has a front end face 25 a facing toward the medium facingsurface 60, and a bottom surface 25 b. As shown in FIG. 1, the front endface 25 a of the second yoke portion 25 includes a first portion 25 a 1,and further includes a second portion 25 a 2 and a third portion 25 a 3located on opposite sides of the first portion 25 a 1 in the track widthdirection. The first portion 25 a 1 is shaped to be recessed such thatthe track-widthwise center of the first portion 25 a 1 is farthest fromthe medium facing surface 60. The first portion 25 a 1 is disposed tosurround the main pole 22. The second and third portions 25 a 2 and 25 a3 are located in the medium facing surface 60 at positions on oppositesides of the first end face 22 a of the main pole 22 in the track widthdirection.

As shown in FIG. 1, the bottom surface 25 b of the second yoke portion25 includes a first portion 25 b 1 that is located farther from themedium facing surface 60 than is the main pole 22, and further includesa second portion 25 b 2 and a third portion 25 b 3 located on oppositesides of the main pole 22 in the track width direction. The secondportion 25 b 2 of the bottom surface 25 b is contiguous with the secondportion 25 a 2 of the front end face 25 a. The third portion 25 b 3 ofthe bottom surface 25 b is contiguous with the third portion 25 a 3 ofthe front end face 25 a. Each of the second and third portions 25 b 2includes an inclined portion inclined relative to the top surface 1 a ofthe substrate 1. The distance from the top surface 1 a of the substrate1 to an arbitrary point on the inclined portion increases withincreasing distance from the arbitrary point to the medium facingsurface 60.

The second and third columnar portions 23 and 24 are located near themedium facing surface 60 and lie on opposite sides of the core 14 andthe plasmon generator 17 in the track width direction. The second andthird columnar portions 23 and 24 penetrate the cladding layers 13, 15and 16 and the dielectric layers 18 and 20, and connect the shield 11and the second yoke portion 25 to each other. Each of the second andthird columnar portions 23 and 24 has a front end face located in themedium facing surface 60, a top surface, and a bottom surface. Thebottom surface of the second columnar portion 23 is in contact with aportion of the top surface 11 c of the shield 11 that is included in thefirst side portion 11B. The bottom surface of the third columnar portion24 is in contact with a portion of the top surface 11 c of the shield 11that is included in the second side portion 11C.

The insulating layer 21 has a first opening for exposing the top surfaceof the second columnar portion 23 and a second opening for exposing thetop surface of the third columnar portion 24. The inclined portion ofthe second portion 25 b 2 of the bottom surface 25 b of the second yokeportion 25 is in contact with the top surface of the second columnarportion 23 through the first opening of the insulating layer 21. Theinclined portion of the third portion 25 b 3 of the bottom surface 25 bof the second yoke portion 25 is in contact with the top surface of thethird columnar portion 24 through the second opening of the insulatinglayer 21. The distance from the top surface 1 a of the substrate 1 to anarbitrary point on the top surface of each of the second and thirdcolumnar portions 23 and 24 increases with increasing distance from thearbitrary point to the medium facing surface 60.

The thermally-assisted magnetic recording head further includes aninsulating layer 26 disposed around the main pole 22 and the second yokeportion 25. The insulating layer 26 is formed of alumina, for example.

The thermally-assisted magnetic recording head further includes a firstyoke portion 34 and a first columnar portion 28 each formed of amagnetic material. The first yoke portion 34 includes a first layer 34Aand a second layer 34B. The first layer 34A lies on the main pole 22.The first columnar portion 28 lies on the second yoke portion 25. Thefirst layer 34A has an end face facing toward the medium facing surface60 and located at a distance from the medium facing surface 60. Thefirst columnar portion 28 has a first end 28 a and a second end 28 bopposite to each other in the direction of travel of the recordingmedium 80. In the present embodiment, the first end 28 a is an end ofthe first columnar portion 28 located on the trailing side or the frontside in the direction of travel of the recording medium 80, whereas thesecond end 28 b is an end of the first columnar portion 28 located onthe leading side or the rear side in the direction of travel of therecording medium 80.

The thermally-assisted magnetic recording head further includes a coil29 wound around the first columnar portion 28. As shown in FIG. 5, thecoil 29 is wound approximately three turns around the first columnarportion 28. The coil 29 is formed of a conductive material such ascopper. The shape and location of the coil 29 will be described indetail later.

The thermally-assisted magnetic recording head further includes aninsulating film 30 isolating the coil 29 from the first layer 34A andthe first columnar portion 28, an insulating layer 31 disposed in thespace between adjacent turns of the coil 29, an insulating layer 32disposed around the first layer 34A and the coil 29, and an insulatinglayer 33 lying on the coil 29, the insulating film 30 and the insulatinglayer 31. The insulating film 30 and the insulating layers 31 to 33 areformed of alumina, for example.

The second layer 34B of the first yoke portion 34 lies on the firstlayer 34A, the first columnar portion 28 and the insulating layer 33.The second layer 34B has an end face facing toward the medium facingsurface 60 and located at a distance from the medium facing surface 60.

As shown in FIG. 5, the thermally-assisted magnetic recording headfurther includes a lead layer 35. The lead layer 35 is located fartherfrom the medium facing surface 60 than is the second layer 34B of thefirst yoke portion 34 and lies on the insulating layer 33. The leadlayer 35 is used for energizing the coil 29, penetrates the insulatinglayer 33 and is electrically connected to the coil 29. The lead layer 35is formed of a conductive material such as copper.

The thermally-assisted magnetic recording head further includes aninsulating layer 36 disposed around the second layer 34B of the firstyoke portion 34 and the lead layer 35, and a protective layer 37disposed to cover the second layer 34B, the lead layer 35 and theinsulating layer 36. The insulating layer 36 and the protective layer 37are formed of alumina, for example.

The parts from the shield 11 to the second layer 34B of the first yokeportion 34 constitute a write head unit. The coil 29 produces a magneticfield corresponding to data to be written on the recording medium 80.The shield 11, the second and third columnar portions 23 and 24, thesecond yoke portion 25, the first columnar portion 28, the first yokeportion 34 and the main pole 22 form a magnetic path for passing amagnetic flux corresponding to the magnetic field produced by the coil29. The main pole 22 allows the magnetic flux corresponding to themagnetic field produced by the coil 29 to pass, and produces a writemagnetic field for writing data on the recording medium 80 by means of aperpendicular magnetic recording system.

As has been described, the thermally-assisted magnetic recording headaccording to the present embodiment includes the medium facing surface60, the read head unit, and the write head unit. The medium facingsurface 60 faces the recording medium 80. The read head unit and thewrite head unit are stacked on the substrate 1. The write head unit islocated on the trailing side, i.e., the front side in the direction oftravel of the recording medium (the Z direction) relative to the readhead unit.

The write head unit includes the coil 29, the main pole 22, the shield11, the waveguide, and the plasmon generator 17. The waveguide includesthe core 14 and the cladding. The cladding includes the cladding layers13, 15 and 16.

As shown in FIG. 3, the write head unit further includes a return pathsection R connecting the main pole 22 and the shield 11 to each otherand allowing a magnetic flux that corresponds to the magnetic fieldproduced by the coil 29 to pass. The return path section R includes thefirst yoke portion 34, the second yoke portion 25, the first columnarportion 28, the second columnar portion 23 and the third columnarportion 24. The return path section R is formed of magnetic materialsince the first yoke portion 34, the second yoke portion 25, the firstcolumnar portion 28, the second columnar portion 23 and the thirdcolumnar portion 24 are all formed of magnetic material.

The main pole 22 has the first end face 22 a located in the mediumfacing surface 60. The shield 11 has the second end face 11 a located inthe medium facing surface 60. The first end face 22 a and the second endface 11 a are located at positions different from each other in thedirection of travel of the recording medium 80 (the Z direction). In thepresent embodiment, the first end face 22 a is located on the front sidein the direction of travel of the recording medium 80 relative to thesecond end face 11 a.

The core 14 has the front end face 14 a located in the medium facingsurface 60. The front end face 14 a is located between the first endface 22 a and the second end face 11 a in the direction of travel of therecording medium 80.

As shown in FIG. 3, the first yoke portion 34, the second yoke portion25 and the first columnar portion 28 are located on the same side in thedirection of travel of the recording medium 80 relative to the core 14.In the present embodiment, the first yoke portion 34, the second yokeportion 25 and the first columnar portion 28 are located on the trailingside or the front side in the direction of travel of the recordingmedium 80 relative to the core 14. As shown in FIG. 3, the firstcolumnar portion 28 is located away from the medium facing surface 60and has the first end 28 a and the second end 28 b. As shown in FIG. 1,the second and third columnar portions 23 and 24 are located closer tothe medium facing surface 60 than is the first columnar portion 28.

The first yoke portion 34 connects one of the main pole 22 and theshield 11 to the first end 28 a of the first columnar portion 28. In thepresent embodiment, the first yoke portion 34 connects particularly themain pole 22 to the first end 28 a of the first columnar portion 28.

The second columnar portion 23 and the third columnar portion 24 arelocated on opposite sides of the plasmon generator 17 in the track widthdirection and connected to the other of the main pole 22 and the shield11, that is, to the shield 11. The second yoke portion 25 is connectedto the second end 28 b of the first columnar portion 28, and connectedto the other of the main pole 22 and the shield 11, that is, to theshield 11 via the second and third columnar portions 23 and 24.

The shield 11 captures a disturbance magnetic field applied to thethermally-assisted magnetic recording head from the outside thereof.This makes it possible to prevent the disturbance magnetic field frombeing intensively captured into the main pole 22 and thereby causingerroneous writing on the recording medium 80. The shield 11 also has thefunction of capturing a magnetic flux that is produced from the firstend face 22 a of the main pole 22 and spreads in directions other thanthe direction perpendicular to the plane of the recording medium 80, andthereby preventing the magnetic flux from reaching the recording medium80. It is thereby possible to increase the write field intensitygradient. The shield 11 and the return path section R also have thefunction of allowing a magnetic flux that has been produced from thefirst end face 22 a of the main pole 22 and has magnetized the recordingmedium 80 to flow back to the main pole 22.

The shape and location of the coil 29 will now be described in detailwith reference to FIG. 5. As shown in FIG. 5, the coil 29 is woundapproximately three turns around the first columnar portion 28. The coil29 includes a coil connection 29E electrically connected to the leadlayer 35, and three conductor portions (hereinafter referred to aslinear conductor portions) 29A, 29B and 29C interposed between the firstcolumnar portion 28 and the medium facing surface 60 and extendinglinearly in parallel to the medium facing surface 60. The linearconductor portions 29A, 29B and 29C are aligned in this order in thedirection perpendicular to the medium facing surface 60, the linearconductor portion 29A being closest to the medium facing surface 60.Each of the linear conductor portions 29A to 29C has a constant width inthe direction perpendicular to the medium facing surface 60 (the Ydirection). In FIG. 5, the positions of opposite ends of each of thelinear conductor portions 29A to 29C in the track width direction (the Xdirection) are indicated in dotted lines. This also applies to otherdrawings that show other linear conductor portions.

An example of the shape of the plasmon generator 17 will now bedescribed with reference to FIG. 2. The plasmon generator 17 has aplasmon exciting part 17 a serving as a bottom surface, a top surface 17b, a front end face 17 c located in the medium facing surface 60, a rearend face 17 d opposite to the front end face 17 c, and two side surfaces17 e and 17 f. The plasmon exciting part 17 a is located at apredetermined distance from the evanescent light generating surface 14 bof the core 14 and faces the evanescent light generating surface 14 b.The cladding layer 16 is interposed between the plasmon exciting part 17a and the evanescent light generating surface 14 b. For example, theplasmon generator 17 is rectangular in cross section parallel to themedium facing surface 60.

The front end face 17 c includes a near-field light generating part 17 glocated at the front extremity of the plasmon exciting part 17 a. Thenear-field light generating part 17 g is located between the first endface 22 a of the main pole 22 and the second end face 11 a of the shield11. In the present embodiment, the first end face 22 a is located on thefront side in the direction of travel of the recording medium 80relative to the near-field light generating part 17 g. The near-fieldlight generating part 17 g generates near-field light on the principleto be described later.

As shown in FIG. 2, the plasmon generator 17 includes a narrow portionlocated in the vicinity of the medium facing surface 60 and a wideportion that is located farther from the medium facing surface 60 thanis the narrow portion. The narrow portion has a front end face locatedin the medium facing surface 60. The front end face of the narrowportion also serves as the front end face 17 c of the plasmon generator17. The width of the narrow portion in the direction parallel to themedium facing surface 60 and to the top surface 1 a of the substrate 1(the X direction) may be constant regardless of the distance from themedium facing surface 60 or may decrease with increasing proximity tothe medium facing surface 60. The wide portion is located on a side ofthe narrow portion farther from the front end face 17 c and is coupledto the narrow portion. The width of the wide portion is the same as thatof the narrow portion at the boundary between the narrow portion and thewide portion, and increases with increasing distance from the narrowportion.

The width (the dimension in the track width direction (the X direction))of the front end face 17 c is defined by the width of the narrow portionin the medium facing surface 60. The width of the front end face 17 cfalls within the range of 5 to 40 nm, for example. The height (thedimension in the Z direction) of the front end face 17 c is defined bythe height of the narrow portion in the medium facing surface 60. Theheight of the front end face 17 c falls within the range of 5 to 40 nm,for example.

An example of the shape of the main pole 22 will now be described withreference to FIG. 3 and FIG. 5. As shown in FIG. 3, the main pole 22 hasthe first end face 22 a, and further has a rear end face 22 b oppositeto the first end face 22 a, and a bottom surface 22 c. The bottomsurface 22 c includes an inclined portion and a flat portion arranged inthis order, the inclined portion being closer to the medium facingsurface 60. The distance from the top surface 1 a of the substrate 1 toan arbitrary point on the inclined portion increases with increasingdistance from the arbitrary point to the medium facing surface 60. Theinclined portion is opposed to a portion of the top surface 17 b of theplasmon generator 17 with the insulating layer 21 interposedtherebetween. The flat portion extends in a direction substantiallyperpendicular to the medium facing surface 60.

As shown in FIG. 5, the main pole 22 includes a narrow portion 22A and awide portion 22B. The narrow portion 22A has an end face located in themedium facing surface 60 and an end opposite to the end face. The wideportion 22B is connected to the end of the narrow portion 22A. The wideportion 22B is greater than the narrow portion 22A in width in the trackwidth direction (the X direction). The width of the narrow portion 22Ain the track width direction is generally constant regardless of thedistance from the medium facing surface 60. The width of the wideportion 22B in the track width direction is the same as that of thenarrow portion 22A at the boundary between the narrow portion 22A andthe wide portion 22B, and gradually increases with increasing distancefrom the medium facing surface 60, then becoming constant. The narrowportion 22A has a length in the range of, for example, 0 to 0.3 μm inthe direction perpendicular to the medium facing surface 60. Where thislength is 0, the narrow portion 22A is not present and thus the wideportion 22B has an end face located in the medium facing surface 60.

The distance between the bottom surface 22 c of the main pole 22 and theevanescent light generating surface 14 b of the core 14 increases withincreasing distance from the medium facing surface 60. This feature ofthe present embodiment makes it possible to prevent the lightpropagating through the core 14 from being absorbed in part by the mainpole 22 and to prevent the surface plasmons excited on the plasmonexciting part 17 a from being absorbed in part by the main pole 22.

Now, the principle of generation of near-field light in the presentembodiment and the principle of thermally-assisted magnetic recordingusing near-field light will be described in detail. Laser light emittedfrom a laser diode (not illustrated) enters the core 14. As shown inFIG. 3, the laser light 50 propagates through the core 14 toward themedium facing surface 60, and reaches the vicinity of the plasmongenerator 17. The evanescent light generating surface 14 b of the core14 generates evanescent light based on the laser light 50 propagatingthrough the core 14. More specifically, the laser light 50 is totallyreflected at the evanescent light generating surface 14 b, and theevanescent light generating surface 14 b thereby generates evanescentlight that permeates into the cladding layer 16. In the plasmongenerator 17, surface plasmons are excited on the plasmon exciting part17 a through coupling with the aforementioned evanescent light. Thesurface plasmons propagate to the near-field light generating part 17 g,and the near-field light generating part 17 g generates near-field lightbased on the surface plasmons.

The near-field light generated from the near-field light generating part17 g is projected toward the recording medium 80, reaches the surface ofthe recording medium 80 and heats a part of the magnetic recording layerof the recording medium 80. This lowers the coercivity of the part ofthe magnetic recording layer. In thermally-assisted magnetic recording,the part of the magnetic recording layer with the lowered coercivity issubjected to a write magnetic field produced by the main pole 22 fordata writing.

The specific functions and effects of the thermally-assisted magneticrecording head according to the present embodiment will now bedescribed. In the present embodiment, the near-field light generatingpart 17 g of the plasmon generator 17 is located between the first endface 22 a of the main pole 22 and the second end face 11 a of the shield11. Part of the core 14 is located in the vicinity of the plasmongenerator 17. The core 14 and the return path section R are configuredto intersect each other without contacting each other. Morespecifically, the second and third columnar portions 23 and 24 of thereturn path section R are located on opposite sides of the core 14 inthe track width direction without contacting the core 14.

In the present embodiment, the first yoke portion 34, the second yokeportion 25 and the first columnar portion 28 of the return path sectionR are located on the same side in the direction of travel of therecording medium 80 relative to the core 14, and the coil 29 is woundaround the first columnar portion 28. The present embodiment allows thefirst columnar portion 28 to be small in width in the track widthdirection regardless of the distance between the respective outer endsof the second and third columnar portions 23 and 24 in the track widthdirection. The present embodiment thus allows the coil 29 to be small inentire length.

In order to improve the write characteristics in a high frequency band,it is desirable that the magnetic path formed by the main pole 22, theshield 11 and the return path section R be reduced in length. To achievethis, it is effective to bring the first columnar portion 28 into closeproximity to the medium facing surface 60. In the present embodiment,the coil 29 is wound around the first columnar portion 28 which is smallin width in the track width direction. Accordingly, even if the firstcolumnar portion 28 is brought into close proximity to the medium facingsurface 60, it is possible to avoid an increase in length of each of thelinear conductor portions 29A to 29C located between the first columnarportion 28 and the medium facing surface 60. The present embodiment thusallows the first columnar portion 28 to be located close to the mediumfacing surface 60 without causing a significant increase in resistanceof the coil 29. Consequently, the present embodiment makes it possibleto reduce the entire length of the coil 29 while reducing the length ofthe magnetic path. The present embodiment is thus able to provide athermally-assisted magnetic recording head that exhibits excellent writecharacteristics in a high frequency band and has the coil 29 of a lowresistance.

Further, the present embodiment allows the coil 29 to have a low heatingvalue because of its low resistance. This makes it possible to preventthe problem that components around the coil 29 may expand to cause partof the medium facing surface 60 to protrude toward the recording medium80 and thus become more likely to collide with the recording medium 80.Further, the present embodiment allows for a reduction in the distancebetween the medium facing surface 60 and the recording medium 80 forimprovements in write characteristics such as the overwrite property.

Now, a method of manufacturing the thermally-assisted magnetic recordinghead according to the present embodiment will be described. The methodof manufacturing the thermally-assisted magnetic recording headaccording to the present embodiment includes the steps of formingcomponents of a plurality of thermally-assisted magnetic recordingheads, except the substrates 1, on a substrate that includes portions tobecome the substrates 1 of the plurality of thermally-assisted magneticrecording heads, thereby fabricating a substructure including aplurality pre-head portions aligned in a plurality of rows, theplurality of pre-head portions becoming individual thermally-assistedmagnetic recording heads later; and forming the plurality ofthermally-assisted magnetic recording heads by cutting the substructureto separate the plurality of pre-head portions from each other. In thestep of forming the plurality of thermally-assisted magnetic recordingheads, the cut surfaces are polished into the medium facing surfaces 60.

Now, with reference to FIG. 6A through FIG. 14B, the method ofmanufacturing the thermally-assisted magnetic recording head accordingto the present embodiment will be described in more detail withattention focused on a single thermally-assisted magnetic recordinghead. FIG. 6A through FIG. 14B each show a stack of layers formed in theprocess of manufacturing the thermally-assisted magnetic recording head.FIG. 6A through FIG. 14B are cross-sectional views each showing part ofthe stack. FIGS. 6A-14A each show a cross section that intersects thefirst end face 22 a of the main pole 22 and that is perpendicular to themedium facing surface 60 and the top surface 1 a of the substrate 1.FIGS. 6B-14B each show a cross section of the stack taken at theposition at which the medium facing surface 60 is to be formed.

As shown in FIG. 6A and FIG. 6B, the method of manufacturing thethermally-assisted magnetic recording head according to the presentembodiment starts with forming the insulating layer 2, the bottom shieldlayer 3 and the bottom shield gap film 4 in this order on the substrate1. Next, the MR element 5 and two leads (not illustrated) connected tothe MR element 5 are formed on the bottom shield gap film 4. The topshield gap film 6 is then formed to cover the MR element 5 and theleads. Next, the top shield layer 7 is formed on the top shield gap film6.

FIG. 7A and FIG. 7B show the next step. In this step, the insulatinglayer 8, the middle shield layer 9 and the nonmagnetic layer 10 areformed in this order on the top shield layer 7.

FIG. 8A and FIG. 8B show the next step. In this step, first, the shield11 is formed on the nonmagnetic layer 10. Next, the insulating layer 12is formed to cover the shield 11. The insulating layer 12 is thenpolished by, for example, chemical mechanical polishing (hereinafterreferred to as CMP), until the shield 11 is exposed.

FIG. 9A and FIG. 9B show the next step. In this step, first, thecladding layer 13 is formed on the shield 11 and the insulating layer12. The core 14 is then formed on the cladding layer 13. Next, thecladding layer 15 is formed to cover the core 14. The cladding layer 15is then polished by, for example, CMP, until the core 14 is exposed.

FIG. 10A and FIG. 10B show the next step. In this step, first, thecladding layer 16 is formed on the core 14 and the cladding layer 15.The plasmon generator 17 is then formed on the cladding layer 16. Next,the dielectric layer 18 is formed to cover the plasmon generator 17. Thedielectric layer 18 is then polished by, for example, CMP, until theplasmon generator 17 is exposed.

FIG. 11A and FIG. 11B show the next step. In this step, first, thecladding layers 13, 15 and 16 and the dielectric layers 18 and 20 areetched by, for example, reactive ion etching or ion beam etching so thattwo openings for exposing the top surface 11 c of the shield 11 areformed on opposite sides of the core 14 in the track width direction.The second and third columnar portions 23 and 24 are then formed in thetwo openings. The second and third columnar portions 23 and 24 areformed such that their respective top surfaces are higher in level thanthe top surface 17 b of the plasmon generator 17 and the top surface ofthe dielectric layer 18. Next, the nonmagnetic metal layer 19 is formedon the plasmon generator 17 and the dielectric layer 18.

FIG. 12A and FIG. 12B show the next step. In this step, first, thedielectric layer 20 is formed on the dielectric layer 18 and thenonmagnetic metal layer 19. Next, the nonmagnetic metal layer 19, thedielectric layer 20, the second columnar portion 23 and the thirdcolumnar portion 24 are taper-etched in part by, for example, ion beametching so as to provide each of the nonmagnetic metal layer 19 and thedielectric layer 20 with the end face mentioned previously, and provideeach of the second and third columnar portions 23 and 24 with the topsurface mentioned previously.

FIG. 13A and FIG. 13B show the next step. In this step, first, theinsulating layer 21 is formed over the entire top surface of the stack.The insulating layer 21 is then etched by, for example, reactive ionetching or ion beam etching so as to provide the insulating layer 21with the first and second openings mentioned previously. Next, the mainpole 22 and the second yoke portion 25 are formed by plating, forexample. At this time, the main pole 22 and the second yoke portion 25may be formed of the same magnetic metal material simultaneously.

FIG. 14A and FIG. 14B show the next step. In this step, first, theinsulating layer 26 is formed to cover the main pole 22 and the secondyoke portion 25. The insulating layer 26 is then polished by, forexample, CMP, until the main pole 22 and the second yoke portion 25 areexposed. Next, the first layer 34A of the first yoke portion 34 isformed on the main pole 22, and the first columnar portion 28 is formedon the second yoke portion 25. The insulating film 30 is then formedover the entire top surface of the stack. Then, the coil 29 and theinsulating layer 31 are formed in this order. Next, the insulating layer32 is formed over the entire top surface of the stack. The insulatingfilm 30 and the insulating layer 32 are then polished by, for example,CMP, until the first layer 34A, the first columnar portion 28, the coil29 and the insulating layer 31 are exposed.

Next, the insulating layer 33 is formed on the coil 29, the insulatingfilm 30 and the insulating layer 31. The insulating layer 33 is thenselectively etched to form therein an opening for exposing the coilconnection 29E (see FIG. 5) of the coil 29. Next, the second layer 34Bof the first yoke portion 34 is formed on the first layer 34A, the firstcolumnar portion 28 and the insulating layer 33. Further, the lead layer35 (see FIG. 5) is formed on the coil connection 29E and the insulatinglayer 33. Next, the insulating layer 36 is formed to cover the secondlayer 34B and the lead layer 35. The insulating layer 36 is thenpolished by, for example, CMP, until the second layer 34B and the leadlayer 35 are exposed.

Next, the protective layer 37 is formed to cover the second layer 34B,the lead layer 35 and the insulating layer 36. Wiring, terminals, andother components are then formed on the top surface of the protectivelayer 37. When the substructure is completed thus, the substructure iscut to separate the plurality of pre-head portions from each other, andthen formation of the medium facing surface 60 by polishing, fabricationof flying rails, and so on are performed to complete thethermally-assisted magnetic recording head.

Second Embodiment

A thermally-assisted magnetic recording head according to a secondembodiment of the invention will now be described with reference to FIG.15 to FIG. 19. FIG. 15 is a perspective view showing the main part ofthe thermally-assisted magnetic recording head. FIG. 16 is a front viewshowing the main part of the thermally-assisted magnetic recording head.FIG. 17 is a cross-sectional view showing the configuration of thethermally-assisted magnetic recording head. FIG. 18 is a front viewshowing the medium facing surface of the thermally-assisted magneticrecording head. FIG. 19 is a plan view showing a part of thethermally-assisted magnetic recording head.

The configuration of the thermally-assisted magnetic recording headaccording to the present embodiment differs from that of the headaccording to the first embodiment in the following ways. Thethermally-assisted magnetic recording head according to the presentembodiment includes a shield 40 formed of a magnetic material, in placeof the shield 11. The shield 40 is located near the front end face 14 aof the core 14. The insulating layer 12 is not provided in the presentembodiment. The cladding layer 13 lies on the nonmagnetic layer 10.

The connections between the shield 40 and the return path section R arethe same as those between the shield 11 and the return path section R inthe first embodiment. Specifically, the second and third columnarportions 23 and 24 of the return path section R are connected to theshield 40. The second yoke portion 25 of the return path section R isconnected to the shield 40 via the second and third columnar portions 23and 24.

The shapes and locations of the shield 40 and the core 14 will now bedescribed in detail with reference to FIG. 15 and FIG. 16. The shield 40has a second end face 40 a located in the medium facing surface 60, arear end face 40 b opposite to the second end face 40 a, and a topsurface 40 c. The shield 40 is shaped to be greater in dimension in thetrack width direction (the X direction) than in dimension in thedirection perpendicular to the top surface 1 a of the substrate 1 (the Zdirection).

The first end face 22 a of the main pole 22 and the second end face 40 aof the shield 40 are located at positions different from each other inthe direction of travel of the recording medium 80 (the Z direction). Inthe present embodiment, in particular, the first end face 22 a islocated on the front side in the direction of travel of the recordingmedium 80 relative to the second end face 40 a. The near-field lightgenerating part 17 g is located between the first end face 22 a and thesecond end face 40 a. As shown in FIG. 16, the distance between thefirst end face 22 a and the second end face 40 a will be represented byreference letter D. The distance D is preferably in the range of 50 to300 nm and more preferably in the range of 50 to 100 nm.

As shown in FIG. 16, the front end face 14 a of the core 14 includes afirst portion 14 a 1 located away from the medium facing surface 60 anda second portion 14 a 2 located in the medium facing surface 60. In thepresent embodiment, the second portion 14 a 2 is located on the rearside in the direction of travel of the recording medium 80 relative tothe first portion 14 a 1. Further, there is a difference in levelbetween the first portion 14 a 1 and the second portion 14 a 2. Notethat the whole of the front end face 14 a may be located away from themedium facing surface 60.

As shown in FIG. 16, the front end face 14 a has a first end E1 and asecond end E2 opposite to each other in the direction of travel of therecording medium 80 (the Z direction). The first end E1 is located onthe front side in the direction of travel of the recording medium 80relative to the second end E2. The first end E1 is thus located closerto the near-field light generating part 17 g than is the second end E2.The first end E1 also serves as the front end of the first portion 14 a1 in the direction of travel of the recording medium 80. The second endE2 also serves as the rear end of the second portion 14 a 2 in thedirection of travel of the recording medium 80.

In FIG. 16, the dotted line indicates the midpoint position between thefirst, end E1 and the second end E2. This midpoint position willhereinafter be represented by reference letter C. Further, the front endface 14 a is divided into two regions: a first region R1 extending fromthe midpoint position C to the first end E1; and a second region R2extending from the midpoint position C to the second end E2. The firstregion R1 includes the first portion 14 a 1 and a part of the secondportion 14 a 2. The second region R2 includes the remainder of thesecond portion 14 a 2.

The shield 40 overlaps only the first region R1 of the front end face 14a of the core 14 when viewed in the direction perpendicular to themedium facing surface 60 (the Y direction). The shield 40 particularlyoverlaps only the first portion 14 a 1 of the first region R1. A part ofthe rear end face 40 b of the shield 40 is opposed to the first portion14 a. The part of the rear end face 40 b may or may not be in contactwith the first portion 14 a 1. In the latter case, a part of thecladding may be interposed between the part of the rear end face 40 band the first portion 14 a 1.

The shield 40 includes an overlapping portion 41 which overlaps thefirst region R1 (the first portion 14 a 1) when viewed in the directionperpendicular to the medium facing surface 60, and further includes afirst non-overlapping portion 42 and a second non-overlapping portion 43located on opposite sides of the overlapping portion 41 in the trackwidth direction (the X direction). In FIG. 19, the boundaries betweenthe overlapping portion 41 and the first and second non-overlappingportions 42 and 43 are indicated in broken lines. The overlappingportion 41 includes a first portion 41A and a second portion 41B locatedon opposite sides of the track-widthwise center of the first region R1.The first and second portions 41A and 41B overlap the first region R1(the first portion 14 a 1) when viewed in the direction perpendicular tothe medium facing surface 60. As shown in FIG. 19, each of the first andsecond portions 41A and 41B has a length that is in the directionperpendicular to the medium facing surface 60 and that increases withincreasing distance from the track-widthwise center of the first regionR1. The overlapping portion 41 may include not only the first and secondportions 41A and 41B but also a third portion located between the firstportion 41A and the second portion 41B. The length of the third portionin the direction perpendicular to the medium facing surface 60 isconstant regardless of position in the track width direction.

The first and second non-overlapping portions 42 and 43 are located onopposite sides of the front end face 14 a of the core 14 in the trackwidth direction when viewed in the direction perpendicular to the mediumfacing surface 60. Thus, the first and second non-overlapping portions42 and 43 do not overlap the front end face 14 a. The maximum length ofeach of the first and second non-overlapping portions 42 and 43 in thedirection perpendicular to the medium facing surface 60 is greater thanthe length of the overlapping portion 41 in that direction. In thepresent embodiment, the second columnar portion 23 is connected to thefirst non-overlapping portion 42. More specifically, the second columnarportion 23 is in contact with a portion of the top surface 40 c of theshield 40 that is included in the first non-overlapping portion 42. Thethird columnar portion 24 is connected to the second non-overlappingportion 43. More specifically, the third columnar portion 24 is incontact with a portion of the top surface 40 c of the shield 40 that isincluded in the second non-overlapping portion 43.

The top surface 40 c of the shield 40 and the evanescent lightgenerating surface 14 b of the core 14 are coplanar. Alternatively, thetop surface 40 c and the evanescent light generating surface 14 b may belocated at different levels in the direction of travel of the recordingmedium 80 (the Z direction). The plasmon exciting part 17 a of theplasmon generator 17 is located at a predetermined distance from each ofthe top surface 40 c and the evanescent light generating surface 14 b,and faces the top surface 40 c and the evanescent light generatingsurface 14 b. A part of the cladding layer 16 is interposed between theplasmon exciting part 17 a and each of the top surface 40 c and theevanescent light generating surface 14 b.

The specific functions and effects of the thermally-assisted magneticrecording head according to the present embodiment will now bedescribed. The shield 40 of the present embodiment has the samefunctions as those of the shield 11 described in the first embodimentsection. Specifically, the shield 40 has the functions of capturing adisturbance magnetic field applied to the thermally-assisted magneticrecording head from the outside thereof; capturing a magnetic flux thatis produced from the first end face 22 a of the main pole 22 and spreadsin directions other than the direction perpendicular to the plane of therecording medium 80, and thereby preventing the magnetic flux fromreaching the recording medium 80; and allowing a magnetic flux that hasbeen produced from the first end face 22 a of the main pole 22 and hasmagnetized the recording medium 80 to flow back to the main pole 22.

In the present embodiment, when viewed in the direction perpendicular tothe medium facing surface 60, the shield 40 overlaps only the firstregion R1 of the front end face 14 a of the core 14, the first region R1being located closer to the main pole 22 than the other region of thefront end face 14 a. The present embodiment thus allows the first endface 22 a of the main pole 22 and the second end face 40 a of the shield40 to be located closer to each other than in the first embodiment. Morespecifically, the present embodiment allows the first end face 22 a andthe second end face 40 a to be in close proximity to each other easilyso that the distance D falls within the range of 50 to 300 nm.Consequently, the present embodiment allows the above-describedfunctions of shield 40 to be effectively exerted to increase the writefield intensity gradient. The lower limit of the distance D (50 nm) is adistance necessary to place the near-field light generating part 17 gbetween the first end face 22 a and the second end face 40 a. Toincrease the write field intensity gradient, the distance D should be assmall as possible. In view of the foregoing, the distance D ispreferably in the range of 50 to 300 nm and more preferably in the rangeof 50 to 100 nm

In the present embodiment, the near-field light generating part 17 g ofthe plasmon generator 17 is located in the medium facing surface 60 andlies between the first end face 22 a and the second end face 40 a. Thisallows for producing a write magnetic field of a large write fieldintensity gradient in the vicinity of the near-field light generatingpart 17 g. Consequently, the present embodiment allows for an increasein linear recording density.

If the shield 40 and the front end face 14 a of the core 14 are opposedto each other over a large area, the light 50 propagating through thecore 14 may pass through the front end face 14 a and enter the shield40, thereby causing the shield 40 to be heated and expand. This willresult in the problem that the shield 40 will protrude toward therecording medium 80 and thus readily collide with the recording medium80. In order to avoid this problem, the distance between the mediumfacing surface 60 and the recording medium 80 could be increased.However, this would lead to deterioration in write characteristics suchas the overwrite property or to an increase in error rate. In contrastto this, the present embodiment is configured so that the shield 40overlaps only the first region R1 of the front end face 14 a when viewedin the direction perpendicular to the medium facing surface 60. Morespecifically, the shield 40 is not present between at least the secondregion R2 of the front end face 14 a and the medium facing surface 60.The present embodiment thus prevents the shield 40 and the front endface 14 a of the core 14 from being opposed to each other over a largearea, thereby precluding the aforementioned problem.

To preclude the aforementioned problem with higher reliability, theregion of the front end face 14 a that the shield 40 overlaps whenviewed in the direction perpendicular to the medium facing surface 60may be only a region extending from a position that is located closer tothe first end E1 (not coinciding with the first end E1) than is themidpoint position C to the first end E1.

Further, in the present embodiment, the shield 40 is shaped to begreater in dimension in the track width direction (the X direction) thanin dimension in the direction perpendicular to the top surface 1 a ofthe substrate 1 (the Z direction). Consequently, even though the shield40 overlaps only the first region R1 of the front end face 14 a, it ispossible to connect the second and third columnar portions 23 and 24 totwo portions of the shield 40 that are opposite in the track widthdirection.

In the present embodiment, the shield 40 formed of a magnetic metalmaterial is provided on the leading side of the plasmon generator 17,particularly in the vicinity of the near-field light generating part 17g. Since the top surface 40 c of the shield 40 is located close to theplasmon exciting part 17 a of the plasmon generator 17, surface plasmonsare excited also on the top surface 40 c. Then, the electric line offorce produced by the surface plasmons on the plasmon exciting part 17 aand the electric line of force produced by the surface plasmons on thetop surface 40 c of the shield 40 are coupled to each other in thevicinity of the near-field light generating part 17 g. This produces ahigh-density electric line of force in a narrow area in the vicinity ofthe near-field light generating part 17 g. The spread of the near-fieldlight generated by the near-field light generating part 17 g is therebysuppressed. Thus, the shield 40 of the present embodiment has also thefunction of suppressing the spread of near-field light. By virtue ofthis function, the present embodiment allows for a reduction in trackwidth to achieve an increase in recording density.

Further, in the present embodiment, the overlapping portion 41 of theshield 40 includes the first and second portions 41A and 41B, and thelength of each of the first and second portions 41A and 41B in thedirection perpendicular to the medium facing surface 60 increases withincreasing distance from the track-widthwise center of the first regionR1. These features of the present embodiment make it possible to enhancethe aforementioned function of the shield 16 while preventing magneticflux from being saturated at some midpoint in the shield 40.

A method of manufacturing the thermally-assisted magnetic recording headaccording to the present embodiment will now be described briefly. Themethod of manufacturing the thermally-assisted magnetic recording headaccording to the present embodiment differs from the method according tothe first embodiment in that the shield 11 and the insulating layer 12are not formed and the cladding layer 13, the core 14 and the claddinglayer 15 are formed subsequent to forming the nonmagnetic layer 10.

In the present embodiment, the following steps are performed after thestep of forming the cladding layer 15 and before the step of forming thecladding layer 16. First, a mask having an opening shaped to correspondto the planar shape of the shield 40 is formed on the top surface of thestack. Using this mask as an etching mask, the core 14 and the claddinglayer 15 are then etched in part by, for example, ion beam etching. Thisetching provides the stack with a groove for receiving the shield 40which will be formed later, and forms the first portion 14 a 1 of thefront end face 14 a of the core 14. Next, a magnetic layer that willlater become the shield 40 is formed over the entire top surface of thestack by ion beam deposition, for example. The material for forming thismagnetic layer deposits on the aforementioned groove and on the surfaceof the mask. The deposit on the groove is formed to have a top surfacelocated at a higher level than the evanescent light generating surface14 b of the core 14. The mask is then lifted off. Next, the top surfaceof the magnetic layer is slightly polished by, for example, CMP, untilit reaches the level of the evanescent light generating surface 14 b.This makes the magnetic layer into the shield 40.

The remainder of configuration, function and effects of the presentembodiment are similar to those of the first embodiment.

Third Embodiment

A thermally-assisted magnetic recording head according to a thirdembodiment of the invention will now be described with reference to FIG.20 to FIG. 24. FIG. 20 is a perspective view showing the main part ofthe thermally-assisted magnetic recording head. FIG. 21 is across-sectional view showing the configuration of the thermally-assistedmagnetic recording head. FIG. 22 is a front view showing the mediumfacing surface of the thermally-assisted magnetic recording head. FIG.23 is a plan view showing a coil of the present embodiment. FIG. 24 is aplan view showing a part of the thermally-assisted magnetic recordinghead.

The configuration of the thermally-assisted magnetic recording headaccording to the present embodiment differs from that of the headaccording to the first embodiment in the following ways. Thethermally-assisted magnetic recording head according to the presentembodiment includes a coil 48, a shield 53 and a lead layer 55 in placeof the coil 29, the shield 11 and the lead layer 35, respectively, ofthe first embodiment. The coil 48, the shield 53 and the lead layer 55are formed of the same materials as those of the coil 29, the shield 11and the lead layer 35, respectively.

The return path section R of the present embodiment includes a firstyoke portion 45, a second yoke portion 54, a first columnar portion 47,a second columnar portion 57 and a third columnar portion 58 in place ofthe first yoke portion 34, the second yoke portion 25, the firstcolumnar portion 28, the second columnar portion 23 and the thirdcolumnar portion 24, respectively, of the first embodiment. The firstyoke portion 45, the second yoke portion 54, the first columnar portion47, the second columnar portion 57 and the third columnar portion 58 areeach formed of a magnetic material.

The first yoke portion 45 includes a first layer 45A and a second layer45B. The first layer 45A lies on the nonmagnetic layer 10. Both thesecond layer 45B and the first columnar portion 47 lie on the firstlayer 45A. The second layer 45B is located near the medium facingsurface 60. The first columnar portion 47 is located farther from themedium facing surface 60 than is the second layer 45B. Each of the firstlayer 45A and the second layer 45B has an end face located in the mediumfacing surface 60. The first columnar portion 47 has a first end 47 aand a second end 47 b opposite to each other in the direction of travelof the recording medium 80. In the present embodiment, the first end 47a is an end of the first columnar portion 47 located on the leading sideor the rear side in the direction of travel of the recording medium 80,whereas the second end 47 b is an end of the first columnar portion 47located on the trailing side or the front side in the direction oftravel of the recording medium 80.

The shield 53 lies on the second layer 45B. The shield 53 has a secondend face 53 a located in the medium facing surface 60 and a rear endface 53 b opposite to the second end face 53 a. The distance from themedium facing surface 60 to an arbitrary point on the rear end face 53 bof the shield 53 decreases with increasing distance from the arbitrarypoint to the top surface 1 a of the substrate 1. As shown in FIG. 24,the shield 53 includes a central portion, and two side portions locatedon opposite sides of the central portion in the track width direction(the X direction). The length of the central portion in the directionperpendicular to the medium facing surface 60 is constant regardless ofposition in the track width direction. The maximum length of each of thetwo side portions in the direction perpendicular to the medium facingsurface 60 is greater than the length of the central portion in thatdirection.

As shown in FIG. 23, the coil 48 is wound approximately three turnsaround the first columnar portion 47. The coil 48 includes a coilconnection 48E electrically connected to the lead layer 55, and threelinear conductor portions 48A, 48B and 48C interposed between the firstcolumnar portion 47 and the medium facing surface 60 and extendinglinearly in parallel to the medium facing surface 60. The linearconductor portions 48A, 48B and 48C are aligned in this order in thedirection perpendicular to the medium facing surface 60, the linearconductor portion 48A being closest to the medium facing surface 60.Each of the linear conductor portions 48A to 48C has a constant width inthe direction perpendicular to the medium facing surface 60 (the Ydirection).

The insulating layers 12, 31, 32, 33 and 36 and the insulating film 30are not provided in the present embodiment. Instead, thethermally-assisted magnetic recording head according to the presentembodiment includes a first insulating layer (not illustrated) lying onthe nonmagnetic layer 10 and surrounding the first layer 45A, aninsulating film 49 isolating the coil 48 from the second layer 45B andthe first columnar portion 47, an insulating layer 51 disposed in thespace between adjacent turns of the coil 48, a second insulating layer(not illustrated) disposed around the second layer 45B and the coil 48,an insulating layer 52 lying on the coil 48, the insulating film 49 andthe insulating layer 51, and an insulating layer 56. The insulating film49, the insulating layers 51, 52 and 56, the first insulating layer, andthe second insulating layer are formed of alumina, for example.

The second yoke portion 54 lies on the first columnar portion 47 and theinsulating layer 52. As shown in FIG. 24, the lead layer 55 is locatedfarther from the medium facing surface 60 than is the second yokeportion 54, and lies on the insulating layer 52. The lead layer 55 isused for energizing the coil 48, penetrates the insulating layer 52 andis electrically connected to the coil connection 48E of the coil 48. Theinsulating layer 56 is disposed around the shield 53, the second yokeportion 54 and the lead 15 layer 55. The cladding layer 13 lies on theshield 53, the second yoke portion 54, the lead layer 55 and theinsulating layer 56.

The second and third columnar portions 57 and 58 are located closer tothe medium facing surface 60 than is the first columnar portion 47, andare present on opposite sides of the core 14, the plasmon generator 17and the main pole 22 in the track width direction. The second and thirdcolumnar portions 57 and 58 penetrate the cladding layers 13, 15 and 16,the dielectric layers 18 and 20 and the insulating layers 21 and 26, andconnect the main pole 22 and the second yoke portion 54 to each other.The protective layer 37 is disposed to cover the main pole 22, thesecond columnar portion 57, the third columnar portion 58 and theinsulating layer 26.

In the present embodiment, the first end face 22 a of the main pole 22is located on the front side in the direction of travel of the recordingmedium 80 relative to the second end face 53 a of the shield 53. Thefront end face 14 a of the core 14 and the near-field light generatingpart 17 g of the plasmon generator 17 are located between the first endface 22 a and the second end face 53 a in the direction of travel of therecording medium 80.

In the present embodiment, the first yoke portion 45, the second yokeportion 54 and the first columnar portion 47 are located on the leadingside or the rear side in the direction of travel of the recording medium80 relative to the core 14. The second layer 45B of the first yokeportion 45 and the first end 47 a of the first columnar portion 47 areconnected to the first layer 45A. The shield 53 is connected to thesecond layer 45B. Thus, in the present embodiment the first yoke portion45 connects the shield 53 to the first end 47 a of the first columnarportion 47. The second columnar portion 57 and the third columnarportion 58 are connected to the main pole 22. The second yoke portion 54is connected to the second end 47 b of the first columnar portion 47,and connected to the main pole 22 via the second and third columnarportions 57 and 58.

Like the first embodiment, the present embodiment allows the firstcolumnar portion 47 to be small in width in the track width directionand thereby allows the coil 48 to be small in entire length. Further,like the first embodiment, the present embodiment allows the linearconductor portions 48A to 48C of the coil 48 to be small in length inthe track width direction. Consequently, the present embodiment makes itpossible to bring the first columnar portion 47 into close proximity tothe medium facing surface 60 without causing a significant increase inresistance of the coil 48.

The remainder of configuration, function and effects of the presentembodiment are similar to those of the first embodiment.

The present invention is not limited to the foregoing embodiments, andvarious modifications may be made thereto. For example, in the firstembodiment, the second yoke portion 25 may be connected to the main pole22 while the first yoke portion 34 may be connected to the shield 11 viathe second and third columnar portions 23 and 24. In the secondembodiment, the second yoke portion 25 may be connected to the main pole22 while the first yoke portion 34 may be connected to the shield 40 viathe second and third columnar portions 23 and 24. In the thirdembodiment, the second yoke portion 54 may be connected to the shield 53while the first yoke portion 45 may be connected to the main pole 22 viathe second and third columnar portions 57 and 58.

It is apparent that the present invention can be carried out in variousforms and modifications in the light of the foregoing descriptions.Accordingly, within the scope of the following claims and equivalentsthereof, the present invention can be carried out in forms other thanthe foregoing most preferable embodiments.

What is claimed is:
 1. A thermally-assisted magnetic recording headcomprising: a medium facing surface facing a recording medium; a coilproducing a magnetic field that corresponds to data to be written on therecording medium; a main pole having a first end face located in themedium facing surface, the main pole allowing a magnetic flux thatcorresponds to the magnetic field produced by the coil to pass, andproducing a write magnetic field for writing the data on the recordingmedium by means of a perpendicular magnetic recording system; a shieldformed of a magnetic material and having a second end face located inthe medium facing surface; a return path section formed of a magneticmaterial, connecting the main pole and the shield to each other andallowing a magnetic flux that corresponds to the magnetic field producedby the coil to pass; a waveguide including a core through which lightpropagates, and a cladding provided around the core; and a plasmongenerator including a near-field light generating part located in themedium facing surface, wherein the first end face and the second endface are located at positions that are different from each other in adirection of travel of the recording medium, the near-field lightgenerating part is located between the first end face and the second endface, the plasmon generator is configured so that a surface plasmon isexcited on the plasmon generator based on the light propagating throughthe core, and the near-field light generating part generates near-fieldlight based on the surface plasmon, the return path section includes afirst yoke portion, a second yoke portion, a first columnar portion, asecond columnar portion, and a third columnar portion, the first yokeportion, the second yoke portion and the first columnar portion arelocated on a same side in the direction of travel of the recordingmedium relative to the core, the first columnar portion is located awayfrom the medium facing surface and has a first end and a second endopposite to each other in the direction of travel of the recordingmedium, the second and third columnar portions are located closer to themedium facing surface than is the first columnar portion, the first yokeportion connects one of the main pole and the shield to the first end ofthe first columnar portion, the second columnar portion and the thirdcolumnar portion are located on opposite sides of the plasmon generatorin a track width direction, and connected to the other of the main poleand the shield, the second yoke portion is connected to the second endof the first columnar portion, and connected to the other of the mainpole and the shield via the second and third columnar portions, and thecoil is wound around the first columnar portion.
 2. Thethermally-assisted magnetic recording head according to claim 1, whereinthe core has an evanescent light generating surface that generatesevanescent light based on the light propagating through the core, theplasmon generator includes a plasmon exciting part located at apredetermined distance from the evanescent light generating surface andfacing the evanescent light generating surface, and in the plasmongenerator, the surface plasmon is excited on the plasmon exciting partthrough coupling with the evanescent light generated by the evanescentlight generating surface, the surface plasmon propagates to thenear-field light generating part, and the near-field light generatingpart generates the near-field light based on the surface plasmon.
 3. Thethermally-assisted magnetic recording head according to claim 1, whereinthe core has a front end face facing toward the medium facing surface,and the front end face is located between the first end face and thesecond end face in the direction of travel of the recording medium. 4.The thermally-assisted magnetic recording head according to claim 1,wherein the core has a front end face facing toward the medium facingsurface, the front end face has a first edge and a second edge oppositeto each other in the direction of travel of the recording medium, thefirst edge is located closer to the near-field light generating partthan is the second edge, when the front end face is divided into tworegions: a first region extending from a midpoint position between thefirst edge and the second edge to the first edge; and a second regionextending from the midpoint position to the second edge, the shieldoverlaps only the first region of the front end face when viewed in adirection perpendicular to the medium facing surface, and the second andthird columnar portions are connected to the shield.
 5. Thethermally-assisted magnetic recording head according to claim 4, whereinthe shield includes a first non-overlapping portion and a secondnon-overlapping portion that are located on opposite sides of the frontend face of the core in the track width direction when viewed in thedirection perpendicular to the medium facing surface, the secondcolumnar portion is connected to the first non-overlapping portion, andthe third columnar portion is connected to the second non-overlappingportion.
 6. The thermally-assisted magnetic recording head according toclaim 4, wherein the first end face and the second end face are at adistance of 50 to 300 nm from each other.
 7. The thermally-assistedmagnetic recording head according to claim 1, wherein the first end faceis located on a front side in the direction of travel of the recordingmedium relative to the near-field light generating part, the first yokeportion, the second yoke portion and the first columnar portion arelocated on the front side in the direction of travel of the recordingmedium relative to the core, the first yoke portion connects the mainpole to the first end of the first columnar portion, the second columnarportion and the third columnar portion are connected to the shield, andthe second yoke portion is connected to the shield via the second andthird columnar portions.
 8. The thermally-assisted magnetic recordinghead according to claim 1, wherein the first end face is located on afront side in the direction of travel of the recording medium relativeto the near-field light generating part, the first yoke portion, thesecond yoke portion and the first columnar portion are located on a rearside in the direction of travel of the recording medium relative to thecore, the first yoke portion connects the shield to the first end of thefirst columnar portion, the second columnar portion and the thirdcolumnar portion are connected to the main pole, and the second yokeportion is connected to the main pole via the second and third columnarportions.